Plant tomatoes outside after your last spring frost date, when soil temperature reaches 60°F

The single most important date for planting tomatoes outdoors is your last spring frost date — the average day when freezing temperatures stop for the season in your area. Tomatoes cannot survive frost. Plant them too early and a late cold snap will kill them. The soil also matters: tomato roots need warmth to grow, so wait until soil temperature is at least 60°F, ideally 65°F or warmer.

To find your last frost date, search "last frost date" plus your zip code, or check the USDA Plant Hardiness Zone Map on planthardiness.ars.usda.gov. Once you know the date, count backward two to three weeks — that is when you can safely plant seedlings you started indoors or bought from a nursery. If you are direct-seeding (planting seeds straight in the ground), wait until one week after the frost date, when soil has warmed more.

Timing varies dramatically by region. In southern Florida or southern Texas, the last frost date falls in February or early March, so you can plant in late winter. In the upper Midwest or northern New England, it may not arrive until late May or early June. Planting on the right date for your location is more important than planting early.

Key Takeaways

  • Find your last spring frost date by searching your zip code online or checking the USDA Plant Hardiness Zone Map.
  • Plant tomato seedlings two to three weeks before your frost date, or direct-seed one week after it.
  • Soil temperature should be 60°F or higher; use a soil thermometer to check, or wait until nighttime air temperatures stay above 50°F consistently.
  • Hardening off seedlings (gradually exposing them to outdoor conditions) for 7 to 10 days before planting prevents transplant shock.
  • If frost threatens after you plant, cover seedlings with row covers or blankets on the night of the freeze.

How to find your exact frost date

Your last frost date is specific to your location — sometimes even to your neighborhood if you live in a hilly or coastal area. The USDA Plant Hardiness Zone Map divides the country into zones based on average minimum winter temperatures, and each zone has a corresponding frost date range. Go to planthardiness.ars.usda.gov, enter your zip code, and the map will show your zone and the frost date window.

If you prefer a faster answer, search "last frost date [your city]" in any search engine. Most results will show the date as a calendar day — for example, May 15 for Denver or April 10 for Atlanta. Write this date down or set a phone reminder. Many local extension offices also publish frost date calendars for their counties, which you can find by searching "[your county] cooperative extension."

If you live in a frost-prone area but want to plant earlier, you can use row covers, cloches (clear plastic domes), or cold frames to protect seedlings from unexpected cold snaps. These tools trap heat and can extend your planting window by two to three weeks.

Checking soil temperature before planting

Air temperature and soil temperature are not the same. The air outside might feel warm during the day, but the soil — especially if it was cold and wet all winter — may still be too cold for tomato roots to grow. A soil thermometer costs $10 to $20 and takes the guesswork out. Push it 4 inches into the soil in the morning, wait 10 minutes, and read the temperature. If it is below 60°F, wait another week and test again.

If you do not have a thermometer, a rough rule is to wait until nighttime temperatures stay above 50°F for at least five consecutive days. At that point, soil has usually warmed enough. You can also feel the soil: if it feels cold and clammy, it is not ready. If it crumbles easily and feels warm to the touch, you are closer.

Planting in cold soil slows root growth, delays flowering, and can cause seedlings to sit in the ground for weeks without growing. The few days you save by planting early are lost to slow growth later. Waiting for warm soil actually gets you to harvest faster.

Hardening off seedlings before planting

Seedlings started indoors or bought from a nursery have been in a sheltered environment — no wind, consistent temperature, filtered light. Moving them directly into the garden is a shock. Hardening off means gradually exposing them to outdoor conditions over 7 to 10 days so they toughen up and do not wilt or die when planted.

Start by placing seedlings in a shaded, sheltered spot outdoors for one to two hours. Each day, increase the time outside and move them into more direct light. By day seven or eight, they should be outside all day. On the final days, leave them out overnight if temperatures stay above 50°F. This process thickens the stems, darkens the leaves, and prepares the plant for sun and wind.

If you skip hardening off, seedlings often turn pale, wilt, or stop growing for weeks after planting. The extra week of preparation pays off in faster establishment and stronger plants.

Planting depth and spacing for outdoor tomatoes

When you plant, bury the seedling deeper than it was growing in its pot — up to the first true leaves. Tomatoes can grow roots all along the buried stem, which strengthens the plant. Space seedlings 24 to 36 inches apart, depending on the variety. Determinate (bush) types need less space; indeterminate (vining) types need more.

Dig a hole slightly larger than the root ball, add a handful of compost or balanced fertilizer to the bottom, and set the seedling in. Fill the hole and water deeply. If the seedling is tall and spindly, lay it in the hole at an angle — the buried stem will root and the plant will straighten as it grows.

Water the seedling well after planting and keep the soil consistently moist (not soggy) for the first two weeks while roots establish. Mulch around the base with 2 to 3 inches of straw or shredded leaves to retain moisture and keep soil warm.

What to do if frost threatens after planting

Even after you plant, a late frost can arrive unexpectedly. If the forecast calls for freezing temperatures within a week of planting, cover your seedlings. Row covers (lightweight fabric) or old blankets draped over stakes work well. Leave the covers on during the day if it is cloudy and cold, and remove them when temperatures rise above 50°F so the plants do not overheat.

If frost does damage seedlings — leaves turn black or mushy — do not pull them out when ready. Wait a few days. Many tomatoes recover from light frost damage and will grow new leaves. Only remove the plant if the stem is completely blackened or the damage is severe.

Regional planting timelines

Planting dates vary widely across the country. In the Deep South (southern Louisiana, southern Florida, southern Texas), the last frost date falls in late February or early March, so you can plant in late winter. In the mid-Atlantic and upper South (Virginia, North Carolina, Tennessee), it is typically mid-April to early May. In the Midwest and Northeast, it is late May to early June. In the Pacific Northwest, it is mid-May. In high-altitude areas (Denver, Salt Lake City), it can be as late as mid-June.

If you are new to your area, ask a local nursery or gardener when they plant tomatoes. They will know the local microclimate and any quirks — for example, coastal areas often have later frost dates than inland areas at the same latitude because the ocean keeps temperatures cooler in spring.

Frequently Asked Questions

Can I plant tomatoes before the last frost date if I use a cold frame?

Yes. A cold frame or row cover can protect seedlings from frost and warm the soil, letting you plant one to three weeks earlier. However, the seedlings still need soil warm enough to root — at least 55°F. Check soil temperature even with protection, and be ready to add extra covers if temperatures drop below freezing.

What if I plant too early and frost kills my seedlings?

If seedlings are killed by frost, you will need to replant. This is why waiting for the frost date is safer than guessing. If you have already planted and frost is forecast, cover the plants when ready with blankets or row covers to minimize damage.

Is nighttime temperature or daytime temperature more important for planting?

Nighttime temperature matters more because tomato roots grow slowly in cold soil, even if days are warm. Wait until nighttime temperatures stay above 50°F consistently, and soil temperature is 60°F or higher. A warm day followed by a cold night can still stall growth.

Can I plant tomatoes in containers earlier than in the ground?

Yes, slightly. Container soil warms faster than ground soil because it is exposed to sun on all sides. You can plant in containers one to two weeks before the frost date, but still wait for soil temperature to reach 60°F and protect containers from frost if needed.

What happens if I plant tomatoes too late in the season?

If you plant very late (after mid-summer in most regions), the plants may not have enough time to flower and set fruit before the first fall frost arrives. Check your first fall frost date and count backward 70 to 85 days (the time most tomatoes need to mature). If fewer than 70 days remain, choose a fast-maturing variety or start with larger seedlings rather than seeds.